Cannot inform ArC to instantiate bean in worker thread about quarkus

[mkouba]

CDI/ArC creates beans, by design, on the current thread. The CDI API (jakarta.enterprise.context.spi.Contextual etc.) is not asynchronous so there's no proper way to offload the construction logic to a worker thread and continue when the bean instance is ready. This feature would require a non-trivial API redesign.

A good mitigation strategy is to initialize the beans eagerly (if possible), for example an @ApplicationScoped/@Singleton bean during application start.

If you really need to execute some blocking code in your bean, in @PostConstruct, etc. and it's possible that this bean could be created on an event loop (io thread), then you'll need to offload the logic manually, something like:

import io.quarkus.runtime.BlockingOperationControl;

@RequestScoped
public class MyBean {
   
   @Inject
   Vertx vertx;
   
   @PostConstruct
   void init() {
      if (BlockingOperationControl.isBlockingAllowed()) {
         somethingThatBlocks();
      } else {
          vertx.executeBlocking(() -> {
            // note that request context is not activated here
            somethingThatBlocks();
            return null;
           });
      }
   }

   void somethingThatBlocks() {}

}

And of course, it gets more complicated if you need to synchronize the state, i.e. if the blocking operation initializes some state of the bean.

[quarkus-bot]

/cc @Ladicek (arc), @manovotn (arc), @mkouba (arc)